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Re: Web Rule Language - WRL vs SWRL

From: Bijan Parsia <bparsia@isr.umd.edu>
Date: Fri, 1 Jul 2005 02:09:26 -0400 (EDT)
To: drew.mcdermott@yale.edu, www-rdf-rules@w3.org
Message-Id: <20050701020926.CRU00174@isrmail.isr.umd.edu>

---- Original message ----
>Date: Fri, 1 Jul 2005 00:03:54 -0400
>From: Drew McDermott <drew.mcdermott@yale.edu>  
>Subject: Re: Web Rule Language - WRL vs SWRL   
>To: www-rdf-rules@w3.org
>
>> >> [Bijan Parsia]
>> >> The old Layering Story has been bankrupted in several different
>> >> ways.
>> [me]
>> > I'll take advantage of this crack in the orthodox Wall of Opprobrium
>> 
>> I don't know how you determine your factions, but this really makes no 
>> sense.
>
>Sorry; I admit that my factionometer is not as accurate as it should be.

I think your local muffler shop should be able to do a recalibration :)

>> (The Old Layering Story is that every semantic web language should be a 
>> same syntax semantic extension of RDF. In this current thread, I think 
>> only Jim ever strongly endorsed that approach, and most of the major 
>> proponents, afaict, have weakened or abandoned it. Peter has a paper in 
>> ICJAI showing that it is paradoxical if extended to FOL. I find it a 
>> PITA for OWL and have argued vehemently, with major grade vehemence for 
>> the truth of my PITA pain.
>
>Well, Ian said this a couple of days (and many messages) ago ---
>
>> Regarding the existing layered architecture of OWL, and the proposed 
>> extension to SWRL, nobody (well not me anyway) claims that it is 
>> perfect, and there will (as Holger has pointed out) no doubt be some 
>> compatibility issues between different tools, but the situation is 
>> hardly comparable to the one that is being proposed in the "updated 
>> layer cake": as we have seen, even the very limited degree of 
>> interoperability suggested by this diagram turns out to be a chimera. 
>> In contrast, RDF, OWL and SWRL share a common semantic framework, and 
>> allow for a relatively clean layering: OWL-Lite, OWL-DL and SWRL are 
>> layered on a subset of RDF, but share the same semantics (and it can be 
>> syntactically determined when RDF ontologies are within this subset).
>
>--- so the Old Story can still be wheeled out when needed.

There's a nuance.

>  Again, if
>I have missed a nuance, I apologize.  

Apology accepted.

> As far as I can tell, "layering"
>is completely meaningless, but perhaps there are degrees of
>meaninglessness.

Perhaps the real issues is that meaninglessness things can be written into 
charters and then force a group to act as if they had meaning...which is nasty.

>> [...]
>> Well, this is familiar from you, Drew, and good to have it on the 
>> table. However, I don't think either Ian nor I are arguing against 
>> non-mon *per se*. I might argue against quasi-proceduralism, but that 
>> doesn't put me on a different side than Michael, as far as I know.
>
>I guess I should have kept my mouth shut, because obviously I don't
>understand the argument.

Well, given MIchael's reply, evidently I don't understand *his* argument, or, it 
may see, yours. So I guess I should have kept *my* mouth shut.

[snip]
>> I wonder what you think of all the work in formal semantics for LP. 
>> Minimal model, perfect model, Well founded, answer set....
>
>Here's the nub: We are in the presence of an unfortunate pun.  All of
>these different "semantics" for LP concern the meaning of logic
>programs _as programs_.  But for interoperability what we care about
>is the semantics of logical expressions as _statements_.  So when Ian
>says 

Ok. That seems to accord with what Michael said in the follow up. I'm not sure I 
buy it, but ok.

>> This isn't the argument: the argument is about (lack of) 
>> interoperability between two formal systems. No one is (yet) claiming 
>> that either of these systems is pixie dust.
>
>I am somewhat baffled.  If two systems use the same syntax, and employ
>the same vocabulary with the same (Tarskian) semantics, then they can
>interoperate by exchanging messages.  The fact that they may have used
>different methods in order to arrive at their conclusions is
>important, but has nothing to do with interoperability per se.  (I'll
>anticipate the objection that there has to be a standard proof or
>justification language so that a module needn't believe a statement
>unaccompanied by a proof; a Methodist system can refuse to believe the
>testimony of a Baptist system.  Having anticipated it, I will simply
>say that I am deeply skeptical about the possibility of such a
>justification system.)

If I send a message intending for it to be understand *as a program* and you 
receive it understanding it *as statement*, then it seems that we have a 
divergence in understanding. Perhaps this is trivial, as MIchael said, or is 
swamped by other facts about my interpretation context. I don't think that 
requires an accompanying justification or proof.

>> [...]
>> I'll be interested to know if Michael thinks this is a defense of him :)
>
>Yes, he's probably preparing a statement disavowing everything I've
>said.  Well, I tried.

You tried better than I thought :) He seems to think you're on the money!

>> I guess I just find this too vague to get a grip on. What's your 
>> proposal? Is ISO Prolog a reasonable starting place? Some more modern 
>> logic/functional programming language? Should we just add a few things 
>> to XQuery?
>>
>> I just don't know how to take your POV and generate useful 
>> standardization activities. Do you think there are none? (That's not 
>> unreasonable.)
>
>My proposal is type theory, or, failing that, Common Logic with a
>strongly typed syntax in front of it.

How about LF?

>   But this is a proposal for a
>notation for exchanging information, not for a system of inference.

What don't you get from XML and XML Schema? Or XQuery. (XML Schema is *a* 
type theory, so perhaps it's not sufficiently flexible (though, I think it's pretty 
expressive what with regex types. But it could be augmented.)

Cheers,
Bijan Parsia..
Received on Friday, 1 July 2005 06:09:33 GMT

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